Shock absorber



F'., 25, i936., E, F. ROSSMAN MAME SHOCK ABSORBER Filed June 18, 1932 2 Sheets-Sheet l .Feb 259 E936. E g.-` ROSSMAN 2,@3283 SHOCK ABSORBER Filed June 18, 19:52 2 sheets-sheet 2 Patented Feb. 25, 1936 UNITED STATES PATENT OFFICE SHOCK ABSORBER Edwin F. Rossman, Da

yton, Ohio, assignor, by

mesne assignments, to General Motors Corporation, ware Detroit, Mich.,

a corporation of Dela- This invention relates to improvements in hydraulic shock absorbers, particularly of the double-acting type.

Shock absorbersfor motor driven vehicles have been produced in both single and double-acting types, the former resisting only the compression movements of the vehicle springs, the latter resisting both the compression and the rebounding movements of the vehicle springs.

In some of the double-acting types, the shock absorbers resisted both the compression and the rebounding movements of the vehicle vsprings with equal force, while in others the shock absorbers oiered a greater resistance to the rebounding movements of the vehicle springs than to the compression movements thereof.

The present invention has for one of its objects to provide a double-acting hydraulic shock absorber with an automatic control device whereby said shock absorber will more greatly resist the rebounding movement of the vehicle .springs than the compression movement thereof.

A further object of the present invention is to provide the double-acting hydraulic shock absorber with hydraulically operated adjusting mechanism so that the shock absorber will adjust itself to provide a greater resistance to the rebounding movements of the Vehicle springs than to the compression movements thereof.

A still further object of the present invention is to utilize the fluid flow in one .direction within the shock absorber, which flow results from the compression movement of the vehicle springs, for purposes of adjusting the fluid ilow control 35 device of the shock absorber to increase the restriction to the iluid flow responsive to both the compression and rebounding movements of the vehicle springs.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred embodiment of one form of the present invention is clearly shown.

In the drawings:

Fig. 1 is a fragmentary side view of the vehicle chassis, the road wheels having been omitted for the sake of clearness, a shock absorber equipped with the present invention being shown secured to the frame of the vehicle.

Fig. 2 is a longitudinal sectional view of the shock absorber showing the uid ilow control devices thereof.

Fig. 3 is a longitudinal sectional View taken through the shock absorber illustrating the reciprocative piston within the shock absorber cylinder.

Fig. 4 is a fragmentary, enlarged sectional view showing the automatic control device of the shock absorber.

Fig. 5 is a fragmentary enlarged sectional view illustrating one of the check valves of the shock absorber.

The shock absorber illustrated in the drawings is adapted to control both the approaching and separating movements of the two relatively movable members, namely the frame and axle of the motor vehicle. In the present drawings the frame of the vehicle is designated by the numeral 2D, said frame being resiliently supported upon 15 the vehicle axle 2| by vehicle springs, one of which is shown at 22. One end of the spring is hingedly secured to the frame as at 23, the other as at 24.

The shock absorber designated as a whole by the numeral 25, comprises a casing 26 (see Figs.

2 and 3) said casing providing a duid reservoir 21 and a cylinder 28 in communication with said reservoir through the opening 29 within the casing. Holes 3U are provided in the casing for re- 25 ceiving studs 3| by means of which the shock absorber 25 is attached to the frame 20 of the vehicle. Both open ends of the cylinder 28 are shown in the present drawings provided with cylinder head caps 32 and 33 respectively, said 30 caps being threaded into their respective cylinder ends and having gaskets to prevent fluid leaks.

Within the cylinder 28 there is provided a reciprocative piston 35 having two piston head portions 36 and 3l. The piston head portion 36 35 forms the spring compression control chamber 38 at one end of the cylinder, while piston head portion 3'! forms the spring rebound control chamber 39 at the opposite end of the cylinder.

Each piston head portion is provided with a 40 iluid replenishing valve, and inasmuch as these valves are identical only one will be described detailedly.

The head portion has a through passage 40 providing communication between the reservoir and the respective compression chamber. A reduced portion in the passage 40 forms a valve seat 4| upon which the ball check valve 42 is urged by a spring 43. It may be seen that the ball check valve will prevent uid from flowing from the respective compression chamber to the reservoir as the piston moves to exert pressure upon the fluid within its compression chamber, however, the valve will act to establish a flow from the reservoir 21 through the passage 40 into 55 20 during the compression ofthe spring .the Vpiston causes the head portion 31 Yterior threads as at 6|.

the respective compression chamber as the pis- 'ton is moved to increase the area of its respective compression chamber.

A space is provided between the piston'head One end of the rocker shaft 5| extends outside the casing 26 and has the shock absorberoperating arm 53 provided thereon. VThe free end of said arm is swivelly attached to one end o a link 54, the opposite end er" said link being swivellyV secured to abracket 55 Vwhich lis clamped upon the axle 2| the clamping member 56.

From this it may be seen that the rockerarmV 56 is operatively connected with the axle 2| and will be cscillated in response to and-in accordance with the movement of said axle. More specically, when the axle2l is moved toward the frame Y 22, link 54 and arm 53 will cause a clockwise rotation of the shaft 5| and rocker arm 50 and consequently a moving of'the piston 35 toward the left as egards Figs. 1,72V and V3. This results in pressure being exerted by the piston head 36 upon theV fluid Within the spring compression control chamber 38, on the other hand, as the axle 2| Vmoves on its separating movement from the trame 20 or during the rebounding movement the vehicle springs 22, movement of the shaft 5| and rocker arm 50 will be reversed and consequently piston 35 will be moved toward the right as regards Figs. l, 2 and 3. This movement of tc exert pressure upon Ythe uid within the spring rebound control chamber'39. V

Means are provided in the shock absorber casing 26 for the transfer of fluid from one compression chamber into the other in response to the reciprocations of the piston 35. This means will now Vbe described detailedly.

' Within the casing 26 there is provided a recess 60 formng'a valve-chamber." One end of this valvechamber epens to the outside of the shock absorber, as shown in Figs. 2 and`4. Adjacent the inner end of this recess 60 are provided in- Two other recesses are provided inthe casing, one designated by the numeral 62, the other by the numeral 63. Both these recesses have interior threads for purposes tc be described. f Y

A duct 65 leads from the spring compression control chamber 38 into the recess 60. An ex= tension of this duct 65 leads from the opposite side of recess 60 into the recess or chamber 63 Yas shown in Fig. 2. A passage Y66 leading from the chamber 62 communicates with a passage 61 which leads from the chamber 63, both said passages 66 and 61 communicating with -therrecess 60. 'Another duct 68 leads `from the recess or chamber 62 into the inner end of the recess 66'.

Still another Aduct 69 shown in d otted lines, provides communication between the recess or chamber 62 andthe spring rebound control chamber 39. Y Y

Various valve seats are provided at'point's of communicationrbetween the various passages or ducts with their respective chambers. One of these valve seats,cdesignatecd by the numeral 10 is ormed where'the passage or duct 68 Vopens into the inner end ci the recess 60. Another valve seat 1| is provided at the point of commu--V vnication between passage 66 and the chamber 62, whilera similar seat 12 is formed at thepoint of communication between passage 61 and the channel 63. Y

The check valve mechanism heusedwithin the recess or chamber 62 will now Vbe described. A Vrecessed screw plug is received Within the threaded end of the recess 62. Cooperating with valve-seat 1| isa valve 3| having a tubular body Vportion slidably supported on the valve stem Y82,

the valve 8| being urgedupon its seat by the spring 83 which is interposed between the valveV 8| and a Washer 84 secured to the'valveV stem 82 and seated in the bottom of the recess of the screw plug 80 as shown in Fig. 2. Y

bThe check-valve contained within the chamber 63 comprises the following: a screw cap or plugV 86 recessed and similar in construction te Y Vthe plug 80 is received by the threaded end of the recess 63. The valveY 81 is urged upon the seat 12 byra spring 88 Vinterposed. between'the valve 81 and a collar 89 which rests upon an ans nular-'iiange 90 within the screw plug 86.V Bef neath the collar 89 and fitting. into'the annular space formed Vby vthe annular flange 90, is a circular screen member 9i. The space within the screw plug 86 and outside the screen 3|, which space is designated by the numeral 92, 'in com" rnunication` with a iiuid passage 93' in the casing,

saidA fluid passage discharging `into an annularY groove 94 formed in the inner wall of Ythe re cessed portion 60 ofthe casing adjacent its outer end, as is clearly shown in the Figs. 2 andi.

The recess 60 receives .a plug |00 having a head portion which presses a sealing gasket |0| betweenit and the casing 26 to prevent fluid leaks at this point. Thisscrew plug has altubularY portion |02 extending into the recess 60, fitting said recess substantially snugly, the inner end of said tubular portionV having threads operatively engaging the threaded portion 6| ofthe recess. Two annular grooves are provided in the outside surface of this tubular portion Yof the plug |00,

one being designated by the numeral |03, aligning with the annular groove 94 in the casing to provide an annular chamber 99 which, as has been mentioned heretofore, receives fluid from the iiuid passage 93 in communication with the interior of the recessed screw plug 86. The other annular groove designated by the numeral |04, is in alignment with the duct 65 and provides an annular chamber within the recess 60 which is in communication with said duct 65. Side openy ings |05 in the tubular portion |02Y cr" the screw plug |00 provide communicationY between .the

annular space formed by groove |64 and the interior of the tubular portion |02.

Two recesses |06 and |01 are provided in the end of the screw plug |00. BothY of these recesses are interiorly threaded to Yreceive sealing screws |08. Y These sealing screws havevbody portions of such a length that interior chambers |08 and ||0 are formed'ewithin the recesses |06 and |01 respectively. A passage ||2 in the Yscrew Y'plug' |00 provides communication between the Fchamber |09 and the annular chamber 89.vv One Yend of anV angularlyYV bent piece of wire ||3 extends into this passage ||2, .the diameter of this wirel being Vpredetermined so that Ya predetervide an orii'ice of predetermined size to control the fluid flew through said passage ||2'. Another mined space is providedwbetween the wireY and '70 the inner wall of saidpassage |2 thereby to pro-VV to the chamber I|5 within the tubular portion |02 of the plug |00, said opening being provided with a valve-seat adapted to be engaged by the ball check valve I I6 so that said ball check-valve I6 will prevent a fluid flow from inner chamber |09 to the chamber I'I5, but a reverse ow from chamber 5 to inner chamber |09 will be permitted by the movement of said ball-valve II6 from its seat. Another channel II'I, similar to the passage II4, leads from the inner chamber |I to the annular space 99. In this channel there is provided a seat adapt/ed to be engaged by the ball check-valve IIB, said ball checkvalve permitting uid to flow from the annular chamber 99 through the channel III into the inner chamber I I 0, but preventing a reverse flow. A passage II9, similar to passage ||2, connects the chamber with the inner chamber H0, this passage I I9 having one end of an angularly bent wire extending thereinto to provide a fluid flow restricting orifice therein.

A reciprocative piston |2| is slidably supported within the tubular extension |02 of the plug |00. The one end of this piston is solid while the opposite end is recessed as at |22. Thisrecess |22 of the piston |2I has a smaller recess |23 leading therefrom. An annular groove |24 is provided in the outer surface of the piston I 2| and forms an annular space within the tubular portion |02. This annular space is in communication with the recess |23 of the piston through cross passages |25, thus it may be seen that the recessed end |22 of the piston I2I is in communication with duct 65 through the recess |23, cross passages |25, annular space provided by the groove |25, cross passages I 25 in the tubular portion |02 of the plug |00 and the annular space provided by the groove |011 in said tubular portion |02.

The solid end of piston |2I has a lug 200 extending therefrom which is adapted to engage the bottom of the tubular part |02 of the screw plug |00 when the piston is in normal position whereby a space II5 is always provided between said piston and the bottom of tubular partY |02.

At the point of communication between the smaller diameter recess |23 and the recess |22 in the piston I2| a valve-'seat is provided which is engaged by the valve |30. This valve |30 has a stern portion I3| telescopically received by the tubular body portion |32 of the valve |33 which is adapted to engage the seat 10. Both t-hese valves are yieldably urged into engagement with their respective seats by a single spring member |35. Adjacent the end of the recessed portion |22 of the piston transverse openings |36 are provided. It will be noted that the seat I0 for the valve |33 is provided within the casing, said seat being immovable, however, the seat for the valve |30 is provided by the reciprocative piston |2I, this seat being formed by the shoulder presented between the two recessed portions |22 and |23 in 'said piston. Thus the seat for valve |30 is movable longitudinally of the axis of the valves |33 and |30. In the Figs. 2 and 4 the piston I2| is shown in its uppermost extreme position, being moved thereby by fluid pressure, as will be de- -scribed hereinafter. Normally lug 200 of this piston rests upon the inner surface of the tubular part |02 of plug |00, said lug, as has been mentioned, spacing the piston from said plug so as to form a chamber within the tubular portion |02 of the screw plug, which chamber is always in communication with the passages ||9 and |I4 so that the former may discharge into said chamber I5 and the latter may only permit discharge of fluid therefrom. As the piston is moved up-V wardly into the position shown in Figs. 2 and 4, the uid chamber I5 is naturally enlarged as shown in Figs. 2 and Ll.V

The device functions in the following manner: Y In response to the striking by the road wheels of an obstruction in the roadway, the axle 2| will be thrown upwardly toward the frame 20, thereby compressing the vehicle springs 22. As has been mentioned heretofore, this action of the axle causes clockwise rotation of the rocker shaft 5I resulting in a movement of the piston 35 toward the left as regards Figs 1, 2 and 3, the piston thus exerting a pressure upon the fluid within the spring compression control chamber 38. Due to this pressure the fluid is forced from said chamber 38 into the duct 65, being directed against the valves |30 and 8I. The valve 81 cannot move in response to this fluid pressure, however, due to a minimum pressure by spring |35 upon the valve |30 it may move to establish a fluid flow from duct 65 through passages |05 and I 25 into the recess |23, thence past the valve into the recess |22 of the reciprocative piston, thence through passage 66, the fluid pressure moving valve 8| from its seat to establish a flow into the chamber 62 from whence the fluid may iiow through duct 69 into the spring rebound control chamber 39.

In response to the fluid pressure within the spring compression contr-ol chamber 38, fluid will also flow from the chamber B3 through the collar 89, passing through screen 9| into the chamber 92 in screw plug 86, thence through the passage 93 into the annular space 99, thence through thepassage III, around the ball check valve I|8 directly into the chamber I I0 in the plug |00. From here the fluid will fiow through the orice presented in the channel I I9 by the cooperation of the metering wire |20 extending thereinto, the fluid discharging then into the chamber ||5 normally provided between the piston |2I and the bottom of tubular part |02. Unless the fluid pressure is suiicient, piston I2 I will not be moved. However, if the pressure of the fluid ow just described is sufcient, then, during this compression movement of the vehicle springs, the piston |2I will be moved upwardly toward the valve |33 and consequently Valve |30, whose stem I3| telescopically engages the tubular body portion |32 of the valve |33, will be moved toward said valve |33, thereby compressing the spring |35 and consequently causing said spring to urge both valves |30 and |33 upon their seats with a greater pressure. This of course necessitates a greater fluid pressure to move either of the valves from their seats to establish fluid flows. It will be understood that the fluid flow or fluid circulation established in response to the movement of the piston to exert pressure upon the fluid within the spring compression control chamber is substantially the only flo-w that is directed into the chamber I |5 to move the piston I2 I upwardly.

As soon as the springs 22 have reached the limit of their compression, caused bythe particular obstruction being met, they will return toward their normal load position with a rebounding movement, resulting in a reverse movement of the piston or particularly toward the right as regards Figs. l, 2 and 3. Now pressure is being exerted upon the fluid within the spring rebound control chamber 39. Ordinarily this ow is established through the following circuit: From the chamber 39 through duct 69 into the chamber 62, thence through the duct or passage 68 against Y |33 is urged upon its' seat with a substantially the valve I 33 moving the valve to establisha flow`r into the valve chamber 6D, thence through passage 61moving the valve 81 fromzits seat to establish the iow into the chamber 63, thence through theduot E5 and its passage through the elements inv the valve chamber 60 into the'spring compression control chamber 38. IfA the spring compression movement has been slight and the piston I2| hasY not been moved upwardly on thecompression control strokeof Ythe shock absorber, then valve light pressure requiring a comparatively light pressureof fluid throughthe passage- 68 Atolmove. said valve from its seat to establish. the flow to the spring compression control chamber. ll-Iow- 'ever,.if the piston I2I hasv been moved upwardly,

as has been'described, by increasedpressure due to extended or increased accelerations of the spring` action, then"the valve |33 will be urged upon'its seat and at increasedpressure-by spring I35,.thus offering a greater restriction to the ow of fluid Vfrom duct 68 into' theY recess.A or valve chamber 60, thereby causingqthe Vshock absorber to provide a greater resistance to the return movement of thesprings 21 totheir normal load position. Y After the iluid'dischargeinto ther chamber II5 has taken place as has been describedl and thus has-moved the piston I2 I toward its upper posi-v tion in which it increases the tension. of the spring |35 between thevalves |33 andA |30, the ow of this fluid from said chamber |I5is.re. strictedso as to retard the return movement of the piston I2I tonormal position, consequently the increased tension of springY |35. is.. gradually decreased during'the rebound movement of the vehicle springs, or more specicallywhileV the shock absorber piston 35 is moved toward the right as regards Figs. 1, 2 and 3. It will be noted that theY fluid Within the valve chamber II5 may exit through'the passage II4 past the valve H5 into the chamber |99, the discharge from said chamber |09' through the passage -I I2 being'restrictedsby the metering Wire II 3 extending into saidpassage III|`v andproviding a fluid flow restricting orifice therein. From the passage I I2 the fluid enters the annular space 99 and from there flows through the passage or duct 93 into; the chamber 92, then through the screenBI, collar Y89, into the chamber B3. where it joins the main flow of fluid fromthe rebound control chamberj 39,-to the compression rcontrol chamber 38. Y f

From; the aforegoing it may be seenfthatras long as `the shock absorber movements are slight, not sufcient fluidpressure is built up within the fluid chamber II5Y tomove the piston I2I to inlY crease the tension ofthe spring |35, whichfspring urges-the fluid flow control valves |30 Aand |33 upon their lrespective seats. However; whenthe fluid pressure reaches a predetermined value and a sucient flow at a proper velocity isestablished through passage I|9 into the; chamber- IIE, then the piston|2| will be moved from its normal position toward thevalve |33, moving'the valve |39 toward the vaforementioned valve. |33 to compress the'comon control springf |33 which loads both valves, as has beenV mentioned. Y

The discharge ofiluid from chamber I-I5 ybeheath the piston 12| is restricted to a. greater in its spring compressing position. IUnder, theseV oonditionspiston |-2I will load both pressure release valvesand thus greater pressuresffrom both ther spring rebound control rchamber and the spring compression controljchambzrery will be. re.- y5 quired tofmove saidvalves for establishingpres- Y surey relieving flows.

In the present invention.v applicant has provided an hydraulic shock absorber which is Yadaptedto control both the Yapproaching. andv 10i separating movements of.Y a vehicle frameY and` axle, said shock. absorber. having fluid ow re` strictingmeans which are automatically adjustedby a hydraulically operated memberin yresponse to only one. movement of theA shock 15,

absorber whereby the movements' of. the shock absorber will be resisted increasedly.

Applicants control" mechanism comprises an inherent par-t of the shock absorber, that is, Ythe power developed lby the shock absorberl in one stroke is utilized to set into. motionradjusting mechanism which adjusts theV shock absorber increasedly to resist relative movements of.. the vehicle frame and axles.

Whilethe form of embodiment ofV the present 25 invention as herein disclosed, constitutes apreferred form, it is to lie-understood that other forms might be adopted, all coming within the scope of the claims which follow. Y

, What is claimed is as follows: y

1. An hydraulic shock absorbercomprising, in combination, means adapted to circulate fluid inV two directions within said` shock absorber; means'adapted to control said fluidV circulation, Y and means adapted to adjustthe said. control 35 means decreasingly to restrict the circulation in one. direction in responseto the pressure of the l uidcirculation in the other direction..`

2. An hydraulic shock absorber comprising, in combination, means adapted to circula-te uid in two directions within said shock absorber; uid flow control means; and means adapted tobe operated by the pressure of the'fluidcirculating in one direction for setting the. fluid flow control means initially to providefa maximumre- 4.5 striction tothe fluid circulation inthe other direction and gradually decreasing said restriction.

3..Ar 1 hydraulicV shock absorber comprising,

. in combination, Ameans adapted to circulate fluid in two directionsY withinsaid shock absorber.; 50 separate means. for controlling thetfludy circulation in each direction; and means adapted to adjust the one fluid circulation regulating means in response tothe circulation of` fluid in the other direction initially to provide a maximum restriction and gradually reducing said` restriction.

4. An hydraulic shock absorber comprising; in combination, means adapted to circulate fluid in two directions within said shock absorber; separater means for controlling4 the fiuidlcirculation in each direction; and means adapted to be operated by the uid circulation inone direc.- tion for adjusting the means for controlling the fluide circulation inthev other direction to in- 65 crease itsrestriction'to said fluidY circulation.. Y 5..An hydraulic shock absorber adapted` to resist` the approaching and separating f movements ofvtwo. relatively movable members by the restriction of uid lirculation, fluid flow re"- 70 stricting means; actuator means adapted to be operated by the flow of fluid in response to and accordance withv the approaching movement of said: Vrelatively movable members foradjusting said s iiuiolV flowv restrictingmeansgraduallyffto 75 coV increase-its restriction of the uid flow during said approaching movement of said members; and means adapted to retard the return'movement of said actuator means during the separating movement of said members, gradually to diminish the restriction to uid flow.

6. An hydraulic shock absorber adapted to resist the approaching and separating movements of two relatively movable members by the restriction of fluid circulation, a plurality of spring-loaded iiuid flow restricting devices; and means providing a seat for one of said devices and adapted to be actuated by the pressure of the fluid in response to the approaching movement of said relatively movable members for adjusting one of said fluid flow restricting devices relatively to the other gradually to increase the restriction of said other devices to said flow of fluid and to provide for substantially maximum restriction to fluid flow by the adjusted device at the beginning of the separating movement of said members.

7. An hydraulic shock absorber adapted to resist the approaching and separating movements of two relativeley movable members by the restriction of fluid circulation, spring loaded valves for restricting said iluid circulation; and hyfdraulically operated means adapted to be actuated by the circulation of fluid in response to one movement of'said relatively movable mem- 'bers toincreas'e the spring load on' said valves.

8. An hydraulic shock absorber adapted to resist the approaching and separating movements 'of tworelativelyV movable members by the restriction of uid circulation, spring loaded valves for restricting said iluid circulation; and hydraulically operated means adapted to be actuated by the circulation of iiuid in response to the approaching movement of said relatively movable members to increase the spring load on said valves preparatory to the circulation of uid responsive to the separating movement of said members.

9. An hydraulic shock absorber adapted by the restriction of uid circulation in one direction or the other, respectively to resist the approaching or separating movements of two relatively movable members; two valves, normally closed, adapted to restrict said fluid circulation; a spring yieldably urging said valves into circuit closing position; and hydraulically operated means adapted to increase the tension of the spring only during one of the movements of said relatively movable members.

10. An hydraulic shock absorber adapted by the restriction of fluid circulation in one direction or the other, respectively to resist the approaching or separating movements of two relatively movable members; two valves, normally closed, adapted to restrict said uid circulation; a spring yieldably urging said valves into circuit closing position; hydraulically operated means adapted to be moved out of normal position to increase the tension of the spring in accordance with the speed and magnitude of the approaching movement of said relatively movabfe members, and means for retarding the return of said hydraulically operated means to normal position during the separating movement of said members.

11. A hydraulic shock absorber adapted to resist the approaching and separating movements of two relatively movable members by the restriction to uid circulation in one or the other direction respectively, comprising, two oppositely acting pressure release valves; a single spring yieldably urging said valves into normally closed positions; and a hydraulically operated member, providing a valve-seat for one of the valves, and adapted to be actuated by the fluid circulation in one direction to move one of said valves to increase the tension of the spring engaging it.

12. An hydraulic shock absorber adapted to resist the approaching and separating movements of two relatively movable members by the restriction to fluid circulation in one or the other direction respectively, comprising, two oppositely acting pressure release valves; a single spring interposed between said valves, yieldably urging them into fluid iiow shutting off positions; a piston member providing a seat for one of the valves and adapted to be actuated to compress the spring in response to and accordance with the iluid circulation set upI in the shock absorber by the approaching movement of the relatively movable members; and means for retarding the return movement of the piston during the separating movement of said members.

13. A hydraulic shock absorber adapted to resist the approaching and separating movements of two relatively movable members comprising a casing having a cylinder in which a reciprocative piston forms two compression chambers; a valve chamber in the casing; ducts leading from the respective compression chambers into said valve chamber; oppositely acting pressure release valves in said valve chamber; a reciprocative member in said valve chamber adapted, in response to the iow of uid into said valve chamber in one direction to. adjust the. pressure release valves; and

means for retarding the return of the valve adjustment to normal during the W of Iluid into the valve chamber in the other direction.

14. A shock absorber comprising, a casing providing a cylinder in which a reciprocative piston forms two fluid compression chambers; a valve chamber in said casing; two oppositely acting valves in said chamber; ducts leading from the respective compression chambers into said valve chamber, said ducts being normally closed by said valves; a spring interposed between said valves yieldably urging them into duct closing position; a reciprocative piston in said valve chamber engaging one of the valves and forming a iluid chamber at one end of the valve chamber; means providing communication between said fluid chamber and one of the ducts; and a restricted outlet for said uid chamber.

l5. An hydraulic shock absorber comprising, means for circulating uid in two directions through said shock absorber; oppositely acting means for restricting said iiuid circulation; reciprocative means for adjusting said restricting means to vary its restriction to the ow of fluid; means providing for the transfer of uid pressure in one direction against said reciprocative means; and means for retarding the return movement 0I said reciprocative means.

16. An hydraulic shock absorber comprising a. fluid containing cylinder; two pistons in said casing, one forming two compression chambers between which fluid is circulated in either direction in response to pressure exerted upon the iiuid by said piston, the other piston being movable by the iiuid pressure in one of said compression chambers; uid flow control devices for restricting iluid circulation between the compression chambers in either direction, one of said devices being engaged by the last mentioned piston and movable thereby to adjust the degree of the restriction by said devices of uid flow in said vvalise chamber; a Yplug having a tubular ibers.k Y "17. VAn 'hydraulic `Yshock `one directiongbetween isa' jcompressionjchammeans'j forcirciilating in tvvo directions, adjustable means for vcorrtrolling Vsaid Auid circulation; and means adapted .to be actuated by lille pressure of tle fluid `iliovviin one direction Yfor adjusting the vlnidiflovv controlling Ymeans to Y V vary its Yregulation Vofthe flow o'fuid in both directions. if f "118, Anghydrauiic .shockV absorber comprising, 4a casingioroviding a;cylinder`in Which a recipro-V Vcative piston forms two compression chambers;

a'gvalve-daamberfin said casing; :ducts connecting vthe respective compression Achambers With portion extending intoV said valve-chamber said portion vhaving Vside .openings providing comlniunication between the Y`ducts'and Athe Yinterior f said portionf two oppositely .actinglispring Vloaded, pressureV release valves' Yin said valve chamber; a pistn reciprocativeyinrthe jcubular r`portion of the plug forming a fluidgchamber therein, .and providing a Vvalve-seat for one 'ofV the Valves; meansconnecting one of 'the .ducts with said/'fluid chamber; andfvalves in said means, kone of which is adapted; to establish a metered 110W of fluid from said: duct linto `said yfluid chamber as the shock absorber piston moves in one direction, the ther "being adapted to establish a restricted flog?` of 'fluid from saidluid chamber back to the duct as the shockabsorber pis'toncmoves in the other direction,

Y `19. An hydraulic shock Aalmsorduercomprising agotarse absorber '.comprsing,

said valves. Y

the other respectivelA directie-n for adjusting ione -control device relaa jgiluidA containingY casing; *means 'for Acirculating fluidback and Yo-rthwithin saidcas'ing; tvocontrol devices forgrestrictng said `fluid circulation; adjusting ymeans Vengaging `one of said devices and adapted te beioperated vby huid Ynew in oneV tively to the other -tolincrease-the `restriction to..

Vthe flop' of uid by bothr devices; and means fc; regulating the fluid "flow to vand from the-adjusting meanssothatthe flow to said meanslis `less' restricted 'than the ovv'from said means.V

20. An hydraulic shock absorber comprising a fluid containing casing; means for circulating Y fluid back and 'forthwithin said casing.; spring member foroneV of said valves; means 'foi'.direct-V Ving the fluid flow in vneldir'ection against said "valve-'seat member te;V move Vit to `increase Vthe spring 'load onrsaid valves; and'rneans providing "for the gradual return fof ,'saidzvalve-seat for decreasing said spring-'load whilethe fluidis being circulated in `the-voposite'direction.

VEDWIN r'. lRossi/IAN.

ion in `one direction orV ra. r-shiftable valve-seat? 

